1. Field of the Invention
The present disclosure generally relates to an intervertebral implant. More particularly, the disclosure generally relates to an intervertebral implant with an incorporated fastening mechanism including systems and methods for installing the intervertebral implant.
2. Description of the Relevant Art
The human spine is a complex mechanical structure including alternating bony vertebrae and fibrocartilaginous discs that are connected by strong ligaments and supported by musculature that extends from the skull to the pelvis and provides axial support to the body. The intervertebral discs provide mechanical cushion between adjacent vertebral segments of the spinal column and include three basic components: the nucleus pulposus, the annulus fibrosis, and two vertebral end plates. The end plates are made of thin cartilage overlying a thin layer of hard cortical bone that attaches to the spongy, cancellous bone of the vertebral body. The annulus fibrosis forms the disc's perimeter and is a tough outer ring that binds adjacent vertebrae together. The vertebrae generally include a vertebral foramen bounded by the anterior vertebral body and the neural arch, which consists of two pedicles and two laminae that are united posteriorly. The spinous and transverse processes protrude from the neural arch. The superior and inferior articular facets lie at the root of the transverse process.
The human spine is highly flexible, capable of a high degree of curvature and twist in nearly every direction. Genetic or developmental irregularities, trauma, chronic stress, and degeneration, however, can result in spinal pathologies for which surgical intervention may be necessary. A disc may become damaged or diseased, reducing intervertebral separation. Reduction of the intervertebral separation may reduce a height of the disc nucleus, which may cause the annulus to buckle in areas where the laminated plies are loosely bonded. As the overlapping laminated plies of the annulus begin to buckle and separate, circumferential or radial annular tears may occur. Such disruption to the natural intervertebral separation may produce pain, which may be alleviated by removal of the disc and subsequently maintaining the natural separation of the vertebrae. In cases of chronic back pain resulting from a degenerated or herniated disc, removal of the disc becomes medically necessary.
In some instances, a damaged disc may be replaced with a disc prosthesis intended to duplicate the dynamic function of a natural spinal disc. In other cases, it may be desirable to fuse adjacent vertebrae of a human spine together after removal of a disc. This procedure is generally referred to as “intervertebral fusion” or “interbody fusion.” Intervertebral fusion has been accomplished with a variety of techniques and instruments. In some instances intervertebral fusion has been accomplished by placing structural bone or interbody fusion cage implants filled with bone graft material (e.g., morselized bone) within an intervertebral space where the spinal disc once resided. Fusion cage implants have been generally successful in promoting fusion and maintaining suitable disc height. Insertion of fusion cage implants, however, may be difficult. For example, fusion cages inserted from a posterior approach are generally limited in size by the space between the nerve roots which the implant is moved through during insertion. Moreover, as the distance between vertebral end plates is reduced, the height of the intervertebral space is reduced, thereby limited the size of implants introduced into the space, and often requiring distraction (e.g., spreading of the vertebrae) to achieve a suitable separation of the vertebrae.
Intervertebral fusion implants are typically inserted between adjacent vertebrae. Fasteners are typically deployed to couple the implant to one or more of the adjacent vertebrae. Problems occur due to the angle at which fasteners need to be employed through the implant into the adjacent vertebra relative to the patient's body. Fastener insertion instruments frequently interfere with a patient's body (e.g., chest, chin, etc.) due to the obtuse angles at which the instrument must be used relative to the implant and spine. These angles may make it difficult for the instrument to engage the fastener and/or apply sufficient pressure/force to the fastener using the instrument (e.g., especially when C2-C3 or C6-C7 levels are fused). It should be noted that fasteners which are positioned substantially perpendicular to vertebrae endplates provide better resistance to pull-out.
Accordingly, there is a desire to provide an implant technique that provides a simple and reliable solution for intervertebral fusion wherein fasteners are inserted substantially perpendicular to an endplate of a vertebra.